1. Field of the Invention
The present invention relates to devices and methods of support structures for decks, sheds and similar small buildings that are not connected to a frost and heave resistant superstructure, in particular structural post and beam connection devices and methods having a friction release mechanism.
2. Description of the Related Art
Decks and other structures that are supported in the manner to be explained are known in the art as “floating” in the sense that they rest on the surface of the grade and are free to move up or down as the soil expands or contracts annually as a result of frost or imposing loads on a given footing that exceeds the soil bearing capacity. It is this uncontrollable independent movement of each footing that can cause destructive forces to certain connections in the support structure. Some examples of footings for deck structures include concrete piers buried in the soil, helical piers screwed into the ground, or ground spikes impaled into the ground. A problem arises, however, when the bottoms of posts of the deck or structure are rigidly attached to the footings, such as for example via an intermediary post bracket that has a lower appendage embedded into the footing material, usually concrete, and the top ends of posts are securely attached to the underside of beams of the overlying construction by toe-nail screwing methods or metal structural connectors. This is a practical and common way to build a support structure for a floating deck, and in so doing a system is created comprising three elements; the footing and its relative holding power in the soil, the post bracket connecting to the post, and the post connecting to the beam. The connection points between each of these three elements are not designed to have any flexibility when the system is under load or stress in the field. So long as any movement upward or downward in the soil is imposed equally on each footing under each beam that supports the deck or similar construction, the forces imposed on the connection points will be in balance and no connection will be under more or less stress than another. In such a state, there is little if any risk that any of the connection points within the system will break.
As used herein, a frost resistant footing means a pier buried in the soil or support device the underside of which is located below the frost line in the soil. The alternative is a non-frost resistant footing which is located within the frost zone or directly on the surface of the soil. What often occurs in the field with non-frost resistant footings among the prior art is that the connections are put under stress when asymmetrical forces are generated as a result of variable freezing in the soil or variable soil bearing capacity from one footing to the next in a plurality of footings under a single beam.
Thus the forces imposed on any given footing and its elements, as defined earlier, are unequal. This is because each connection among the three elements in the prior art systems is rigid and intentionally designed not to move or flex. The prior art system will hold until the force imposed on any connection surpasses its load capacity, and when this occurs, the weakest link or connection in the system will give way and break. Examples of this would be post to beam connections separating to relieve and balance the stress in the system. Or screws in the post bracket that secure the post may shear in order that the post may lift up out of the post bracket to relieve the stress. Or if none of these connections fail, the footing may be pulled up from the soil. Any of these scenarios is not desirable since the integrity of the structure will have been compromised. The only way to entirely avoid this destructive scenario is to forego the simplicity and cost savings of a floating deck and install frost resistant footings; be they concrete piers with footings extending below the frost line or engineered helical piers which can be screwed in to the ground well below the frost line. In such cases, the deck is no longer floating but rather it is immobile. And because it is immobile, all connection points described above are protected. Such methods require more labor and materials and are considerably more expensive than a floating deck structure. The very desirability of using a floating deck style of construction is to simplify and reduce costs of the construction process. If a floating deck is built using the prior art devices and methods, costs savings and convenience of installation are enjoyed, but the critical connections described that form the support structure system are at risk of failing due to uneven forces acting on the various support connections.
An example of a prior art support system that is not vulnerable to the uneven force issue is taught by Hoffman in U.S. Pat. Nos. 5,392,575, 5,953,874 and 6,609,346. The systems therein do not cause connections to break as described above, but neither do they provide a secure connection between the ground and the support posts. This system comprises a concrete block, sometimes referred in the art as “deck blocks”. These are simple in design and concept and are shaped like a pyramid but with a flat top, wherein there are cavities formed within the top surface in order to fit a post or joist. If one block is lifted by frost and another is not, the post under the beam above the block that did not rise would simply lift up out of the cavity in the block. This ensures no connection is ever broken, but the entire structure is only held in place by its own weight. However, many jurisdictions prohibit the use of such blocks because high winds (for example as in tornado or hurricane situations) may lift the entire deck or may pick up and toss the blocks. Hence, while concrete blocks as taught by Hoffman address one aspect of the problem at hand, they leave structures vulnerable in other ways.
In the field of construction for outdoor structures such as decks, sheds, stair landings and the like, a number of alternatives to traditional concrete piers and large surface area footings (dug into the soil and set so that the underside of said footing is below frost depth) have been developed. These devices have been developed in an effort to avoid the labor and expense of digging holes either for securing posts to the ground for fencing or for supporting structures and bearing weight. The field of prior art devices for post brackets, post spike devices and the like is crowded, therefore it may be helpful to review the progression of the development of the various devices over the last century in order to understand the problems that each device was intended to address. By observing the steady and constant advancement it will be clear to see where the various groupings of devices have headed and also expose new problems that have arisen in different segments of the art and which remain to be adequately solved.
The prior art devices that became the precursors to some of the common structural connectors we now see in the field of wood construction is exemplified by Yeager in U.S. Pat. No. 1,699,557, which resembled an H shape whereby two opposing boards could be connected and firmly held in place within the H shaped vertical and opposing flanges. Small apertures were defined on the flanges to permit nails or screws to be driven perpendicularly through the flange and into the wood board to lock it in place. The boards so joined were not intended to ever move again. A similar device is taught by Krabiel in U.S. Pat. No. 1,816,226, which also shows similar physical characteristics to Yeager but in the form of a U shaped connector. Apertures are defined in the flat surface of the U shaped rather than the vertical and opposite flanges which permit nails or screws to be guided as they are driven into a wooden member. The vertical flanges are then embedded into wet cement and left to cure in place. Bierbach in U.S. Pat. No. 2,191,979 advanced the concept taught in Yeager by introducing various curves and formed convex shapes to the metal. Legs with embossments are present and used to provide better holding power once set into wet cement. A beam is set into the upper vertical flanges and small apertures in these flanges are provided to guide any nails or screws used to secure the beam in the device. In 1973, Howell in U.S. Pat. No. 3,727,358 added to this genre of metal connector by virtue of its unique folding method of manufacture and its ability to compensate for sloped surfaces while orienting a post vertical relative to its surroundings. Common to the Howell device are the numerous apertures for nails or screws locking the post in place and rendering it immobile. In U.S. Pat. No. 4,906,677, Gib teaches a further manufacturing refinement using a single sheet of steel and configured so that two looping appendages could be set into wet cement while providing a stand off base to keep the wood post elevated above the concrete surface and upstanding legs or flanges to encapsulate and hold the post secure with bolts. The post is intended to remain immobile once secured within the anchoring bracket. Structures using this method of anchoring are intended to be stable and immobile by virtue of the concrete footing that the structure rests upon also intended to be immobile.
Further examples of similar style post holder brackets include devices taught by Han in U.S. Pat. No. 4,958,470, Colonias in U.S. Pat. No. 4,995,206, Reed in U.S. Pat. No. 5,143,472 and Leek in U.S. Pat. No. 5,333,435. There are aspects to each device which vary from the other and these tend to be in the way the metal is shaped and bent. But among them all, it is clear to see that they all have very similar upstanding legs or flanges between which a post is cradled and precise circular apertures through which fasteners are aligned and driven into the wood post to lock it in place permanently.
The permanency of the fitting is intended to address the use of the device in the field. All of these solutions are themselves secured permanently to an immobile substrate or footing of concrete. Mobility of the underlying concrete footing is not intended nor is it desirable for the building applications these devices are designed to be used in.
Continuing with a review of the prior art we now move in a slightly different direction where we see a myriad of devices designed to make the installation of fence posts easier and simpler by employing spikes or helixes impaled or screwed into the ground with post brackets on the upper remote end of the device resembling the similar physical features of the earlier prior art discussed. Mills in U.S. Pat. No. 4,588,157 and Brown in U.S. Pat. No. 5,090,656 both employ inwardly directed tangs specifically formed to permit slicing into the material of the post bottom being urged into the cavity of the post bracket. The tangs are intended to secure the post more effectively than screws alone as well as secure posts which may be undersized relative to the post bracket cavity. However, consistent with the prior art, circular apertures are defined in the upper walls of the post bracket for screws or nails to be driven and permanently secure and render the post immobile. Idland in U.S. Pat. No. 4,614,070 uses a means of adjusting the width between the upstanding legs or flanges of the post bracket to adjust to the variance in width from one post to another within a defined range of post sizes. It too uses circular apertures for screws to pass through and permanently affix or lock the post into the post bracket. Meyer (U.S. Pat. No. 6,273,390), Speece (U.S. Pat. No. 5,927,577) and Walker (U.S. Pat. No. 7,219,872) developed post support solutions for driving fence posts into the ground. While all of these devices function as a post ground spike, they all attempt to make it easier to finely adjust the vertical attitude of the post in situations where the spike can not be driven perfectly perpendicular into the ground or if the spike is installed on a slope. They employ various styles of ball joint connections between the lower spike and upper post bracket portion of their respective devices. Common among these three devices is the known prior art post bracket styles of a defined inner cavity with an open portion with flanges at one corner of the defined cavity that can be clamped together thus compressing the cavity walls around the post. Circular apertures are defined in the cavity walls to align screws or nails which may be driven into the post and permanently locking it in place. Opposing flanges at an open corner of the post bracket are also found in the Zhu device (U.S. Pat. No. 8,322,678) although the main advancement with the Zhu device is the concept of using thinner sheet metal for the lower spike appendages and adding stamped and embossed reinforcement lines shapes running along the longitudinal axis of the spike so as to render the thinner metal more rigid.
Other devices which go further in trying to create one size of post support bracket that may fit tighter with a greater range of post sizes are the Hill device (U.S. Pat. No. 7,730,675) and the Callies device (U.S. Patent Publication No. 2005/0279896). Both teach a device whereby impressions are embossed into the vertically defined walls inside of the bracket which hold the post. These impressions protrude inwardly into the cavity of the post bracket from the inside planar surfaces defining the cavity. One variant device from this grouping of prior art devices is the Teeters device (U.S. Pat. No. 4,199,908) which employs an elongated aperture running horizontally so that the post supporting portion of the device may be easily moved horizontally and then affixed at the desired location by nuts and bolts. Vertically opposing and upstanding legs then fit snuggly against the post. Screws or nails may be driven through circular apertures and into the post locking the post permanently in this position. The elongated apertures address the desire of users to have a degree of horizontal motion while determining the final position of the post. But once that final location is found, the post is intended to be precisely but permanently secured in position.
A further nuance among the ground anchor genre of devices is the Boulay device (U.S. Patent Publication No. 2011/0036025). Boulay teaches the use of a helical anchor common among the prior art but with a cap plate with a central circular aperture through which the top threaded remote upper end of the anchor protrudes. The underside of the cap plate rests on the upper surface of an ring integrally formed around upper shaft of the helical anchor rod just below where the threads terminate. The cap plate is compressed against the ring but with two nuts having differing outer diameters above it. A conventional post bracket similar to the prior art devices can be screwed on to the remote end of the threaded rod if a similar threaded female nut or aperture is located underside of the post bracket. Additionally, any other kind of attachment could be screwed onto the threaded rod such as a loop shaped device enabling the device to function as an anchor for guy wires and the like. The claimed unique characteristics of the Boulay device are the two different size nuts which are used to screw tightly together. Once locked together and so long as the fit is very tight with the threads on the rod and the nuts, different sizes of sockets can be fitted over either the larger lower nut or smaller upper nut and drive the anchor downward or upward from the soil. However, the proficiency and reliability of using two nuts to screw tightly against one another along a common inner threaded rod that defines a longitudinal rod with helical blades to screw into the ground and such that the resulting union of the two nuts functions as a fixed point along the rod critically allowing the entire rod to turn forward or reverse is proven to be low. All elements of the union of the nuts, the threads and the rod must function perfectly for the rod to screw down or into the ground and if any element fails such as the nuts turning in unison or in synchronization with each other around the threaded rod or the threads of a single nut or along the rod are stripped, the rod will no longer be capable of being rotated under the driving torque forces of the impact wrench rendering it useless in the field. It has been discovered that the only reliable structure for driving or rotating an anchor such as in Boulay into the ground is to incorporate a direct drive structure integral to the rod itself, such as a square, hexagonal or similar as in the present invention as described and illustrated herein. Lastly, Boulay does not address the problem of uneven vertical movement caused by ground movements, and it does not teach or suggest any structural features in post receiving bracket of his device that would permit the post to move vertically if subjected to soil movement and pressures generated from other natural movement or subsidence. Structures built with the Boulay device would have no means to safely release such energy, and leave at risk any of the critical elements of both the device and the structure that is supports for the possibility of breaking.
The concept of a helical anchor as a ground anchor was also used by Alexander (U.S. Pat. No. 4,803,812) and Cockman (U.S. Pat. No. 4,863,137). Alexander taught the use of a helical anchoring device that could be easily driven into the ground using power tools rather than heavy equipment. A horizontal plate for stabilization or load bearing is integral to the device, not unlike the Boulay device. A prop or vertically oriented tube or solid cylindrical member protrudes upward from a second horizontal platform also integral to the anchoring rod. It is intended for hollow metal posts or wood posts with hollowed cores to be fitted over the prop and thus secured in place. While such a device and method provides a desirable means of attaching posts to the ground with greater ease than the prior art at the time, Alexander does not touch upon the problem of uneven soil movement nor how this device would alleviate the risks of post and beam connections failing were the device to used among a plurality of said devices under a common beam intended to support compressive loads upon soil subject to frost or other natural movements or subsidence. Cockman proposed using a helical anchoring rod similar to the prior art but taught the use of a compression disk integral to the upper remote end of the rod and the use of a post bracket using the common vertical side panels but with the ability to slide in an outward to accommodate varying sizes of posts. The compression disk was intended to compress soil downward after it had been churned by the turning helical blades. The post bracket uses similar design and function attributes seen among the entire prior art. That is to say, opposing vertical flanges between which a post is placed and numerous circular apertures through which screws or nails can be driven through and securing the post into the bracket. The post is permanently secured and the entire anchor and post are intended to never release from one another. Likewise Cockman did not address the issue of soil movement and uneven forces created in system of ground anchored posts. Such forces are known to destroy post and beam connections when footings under a common beam are subject to differing movements.
In 2009, Hill (U.S. Patent Publication No. 2009/0133337) proposed an adaptation to the his earlier device (U.S. Pat. No. 7,730,675). This adaptation utilized a load bearing plate through which the cross shaped fins of the ground spike could fit through. Hill teaches to drive the ground spike into the ground using a sledge or jackhammer thereby compressing the soil underneath the load bearing plate. The larger surface area of the bearing plate spreads the weight of any structure above it over a larger area than if the post anchor spike were used without the plate. As discussed previously, the upper post bracket portion of the device employs inwardly embossed zones to compensate for a known variance in post size and circular apertures through which screws are driven and permanently locking the post into place. The Hill device is a means of installing load bearing posts when the load bearing plate is used. However the Hill device lacks the ability for any single post among a plurality of posts supporting a common beam to release by virtue of a friction triggered method or any other method which would relieve uneven stresses built up in the post, beam and footing system caused by uneven soil movement. As a result decks or other structures using this system in areas where frost of uneven soil bearing capacity exists are subject to the risks of destruction discussed herein.
Although there have been devices and methods taught over nearly a century in the field of ground driven post anchoring means, none of the prior art teaches or contemplates a solution for the problem of uneven soil movement and a simple and effective means of protecting the integrity of the post and beam connections among a plurality of support posts under a common beam. The original use for these devices and their adaptations particularly the ground spikes and helical anchors, was most commonly intended for single fence posts or single ground anchors. However, because of the continued desire to find easier and less expensive means of building footings and foundations for lightweight structures, the use of these prior art devices in situations such as support posts under common beams began to expose their limitations.
Accordingly, there is a need for devices and methods of support structures for decks, sheds, small buildings and similar light weight constructions that are capable of compensating for asymmetrical uplift forces acting on any single footing within a plurality of footings under a common beam such as may occur, for example, due to differing frost conditions in the soil or variable soil bearing capacity.